Grinding machine for twist drills



March 13, 1928.

C. KOBIS GRINDING MACHINE FOR TWIST DRILLS Filed Feb. 14. 1927 2sheets-sheet 1 March 13, 1928. 1,662,521

c. KOBIS GRINDTNG MACHINE FOR TWIST DRILLS Filed Feb. 14, 1927 2Sheets-Sheet 3 Patented Mar. 13, 1928.

UNITED STATES CARL KOBIS, OF BERLIN, GERMANY.

GRINDING MACHINE FOB TWIST DRILLS.

Application filed February 14, 1927, Serial No. 168,144, and in GermanyFebruary 9, 1926.

This invention relates to that type of drill grinder in which a tubularholder. into which the drill fits, and having an abutting stop to engagethe conical surface of-the drill end or lip to limit itsprojection'therethrough is mounted with its axis inclined to an abradingsurface and so as to be movable bodily toward said surfacein a directionnormal thereto, and specifically my invention relates to means (whichmay be supplemental to the ordinary feed screw for ca'us ing such bodilymovement) for producing a limited movement forward or back in the sameline, the limits of which may be prcdetel-mined with a View to securingthat the grinding operation is stopped just the moment the last groundconical surface terfiiinates in the center or axial line of the Inthevdrawings one embodiment of the invention is shown diagrammatically.

Fig. 1 shows the drill just brought into contact with the grinding wheelbefore grinding the first lip, with the point of the drill lying on itscenter line.

Fig. 2 is the position after the first axial adjustment to the fullamount of play.

Fig. 3 is the position before grinding the second'lip.

Fig. 4 shows the position after grinding the second lip.

Fig. 5 shows the eifect ofthe new device.

Fig. 6 is an elevation and partly a vertical section of the improvedgrinding machine,

Fig. 6 is a section taken along the line 66 of Fig. 6, parts beingbroken away.

Fig. 7 is a sectional front View of Fig. 6.

Fig. 8 is a plan View of Fig. 7.

In front of the grinding wheel a is the guide-casing b in a slopingposition, which guide casing holds and guides the twist drill a duringgrinding and has at its foremost end a gaging stop member d for theconical or substantially conical lip of the drill which for the momentis not to be ground.

The drill is inserted in the casing axially in the direction of thearrow, until the free lip comes up against the gaging stop d, whereuponthe turning position of the drill is ensured by the transverse gagingstop.

Then in the usual machines as also in the new machine, by means of theadjusting .spindle 7 (Figs. 68) engaging the work piece sppport, thecasing 5 together with the drill a is radially adjusted against thegrinding wheel until the outer surface or lip to be ground just touchesthe grinding wheel a (Fig. 1). The casing is then again further adjustedby the spindle f to the distance indicated at 7 (Fig. 2), whichrepresents the grinding feed contemplated, and the drill if it has notbeen carried up with the casing is then pushed forward by hand withinthe casing up to the gaging stop at of the casing to effect grinding asin the usual machines. If, in accordance with Fig. 1, the point has lainexactly on the centre line, that is on the axis A-B of the drill andcasing, then owing to the sloping position of the drill relatively tothe wheel, after this first adjustment. and grinding, the point 72.

be at a distance of about 2' from the gaging stop (Z corresponding tothe amount ground on the lip first ground and the amount to be groundoff the second lip.

When the drill, by being pushed forward by hand in the casing is so faradjusted that its lip opposite to the gaging stop (I again contacts withthe gaging stop (1 (Fig. 4), which therefore corresponds to anadjustment to the double amount 2 the point h will again be to the rightof the drill axis A--B, i. e. again out of the centre position, and soon. In this way the drill is roughly ground. the grinding being effectedby swinging the drill round the sloping axis py means of the hand wheelprovided there- The present invention is characterized by the provisionof an auxiliary device which permits, in a simple manner, the easywithdrawal for thefinal grinding by the amount of play between the lippreviously ground and the stop gauge at due to such previous grinding ofthat lip so as not to add this to the amount to be ground oft the secondlip as the bit, is again fed forward the.

casing 6 being preferably drawn back through this distance so that forthe last position. as shown by Fig. 5, it returns to the position shownin Fig. 1. Then if the drill bit he placed with the lip-to be groundtouching the rinding wheel, its other 11p just ground Wlll be a distance9 from stopgage (Z and'the drill can only be forced forward for grindingthis distance, when it will be stopped by engagement with stopgage (1..The point it of the finished drill is then exactly on the centre line(Flg. 5).

The machine will now be further described.

The casing b is pivotally held on a sloping axis in the usual way, bythe member The member 2' is secured to the support In mounted on theslide m. Said slide m engages by means of a slideway at its lower partwith an intermediate plate 11. which is provided with a recess 1elongated transverse the direction of motion of the slide. A pin 0pivotally engages a block w slidable in said recess, said pin 0 beingeccentrically arranged upon an eccentric p. The eccentric p is keyedatthe top into the hub or boss of a. lever g and is rotatably mountedwith- .in an intermediate socket r fixed in the slide m.

The eccentricity between the pin 0 and eccentric p corres onds to thelargest adjustment g for dri ls of the diameter range concerned.

In using the machine, the lever q is first brought into'the position qshown in dotted lines (Fig. 8), in which the slide on takes up itsmiddle position with respect to the plate n. Then, by means of thespindle f, the slide at together with the plate 'n (to which it isconnected by the pin 0. and eccentric p) is adjusted so far that thedrill just touches the grinding wheel a (Fig. 1).

The actual adjustment through the distance g, however, is no longer doneby means of the spindle f,,but the eccentric p is moved by turning thelever from the position (Fig. 8) to the position q to the left (Fig. 8;or to an intermediate position. As the p ate 1:. is then rigidly securedto the body of the machine by the spindle f, it follows that b turningthe eccentric, the slide on with tie support In, the member 2', and thecasing b, are moved to the left through the distance 7, i. e. they aresuitably adjusted for grinding.

In this manner grinding takes place cor responding to Fig. 2, thespindle f and the lever q and consequently also the eccentricallyarranged pin 0, and eccentric p retaining their positions'during thegrinding, whilst through continued oscillation of the drill holder 6around its axis, said axis being kept stationary on account of themember i, the drill is gradually ground down. until the conical orsubstantially conical lip contacts with its gaging sto d. The drill isthen turned round througii 180 and the grinding continued in the sameway until finally the rough grinding is finished. When the position isreached as shown in Fig. 4, i. e. the position prior to the finalgrindin the lever 1 is moved back into the position 9' and thereby theslide m together with the casing b are drawn back through the adjustmentdistance 7 into the position shown in Fig. 5, whereupon the point h ofthe drill is brought by the final grinding exactly onto the centre line.

The. end positions of the lever q and ot the ccccntrically arranged pin0, and eccentric p, and preferably many intermediate positions, arelocated by a fixing device t. This fixing device may consist of notchesadapted to be engaged by spring stops as shown. V

Naturally the eccentrically arranged pivot-s could be replaced by manyother devices, for example by a cone, a coarse thread, or the like.

As the adjustment in previous drill grinding machines was carried outexclusively by means of the support spindle, the movement of which ispractically unlimited, there is always the danger with these machines ofthe workman adjusting too strongly and thus grinding down the casing.This danger is eliminated in the new machine, as in this case theadjustment, in the working operations takes place by means of the pin 0and eccentric p, of fixed or limited throw.

However, the advantages of the invention could be secured, although in aless favourable manner, by usin the spindle only for adjusting, byfixing tfie adjustment distance 9 by means of a suitable snap ball andsocket, a cone stop, a stepped stop, a screw stop or the like,cooperating with the spindle, so that an easy withdrawal to thisdistance prior to the final grinding can also take place.

What I claim is 1. In a twist drill grinding machine, the combinationwith a grinding surface and a drill guide casing mounted oblique to thegrinding plane, a gage-sto arranged to engage the end of the drill lipopposite to the one being ground and a screw spindle for adjusting saidguide casing to and from said grinding surface, a second adjustingmember adapted to adjust said guide casing to and from said grindingsurface and having a predetermined throw or range of action, so that itsreverse action repositions the gage stop to determine on a latergrinding of one lip an amount of reduction equal to that produced by aprevious grinding of the other lip, thereby bringing the point of thedrill accurately into the center.

2. In a twist drill grinding machine, the combination with the grindingsurface, and a drill guide casing mounted oblique to the grinding plane,a gage stop arranged to engage the end of the one hp opposite to the onebeing ground and a screw spindle for adjusting said guide casing to andfrom said grinding surface,a second adjusting'memher-adapted to adjustsaid guide casing to and from said grinding surface and having apredetermined throw or range of action, so that its reverse actionrepositions the gage stop to determine on a later grinding of one lip,an amount of reduction equal to that produced on a previous grinding ofthe other lip, thereby bringing the point of the drill accurately intothe center, said second adjusting member being an eccentric.

3. Ina twist drill grinding machine, the combination with the grindingsurface, a drill guide casing mounted oblique to the grinding plane, agage stop arranged to engage the end of one lip opposite to the onebeing ground and a screw spindle for adjustingsaid guide casing to andfrom said grinding surface, a second adjusting member adapted to adjustsaid guide casing to and from said grinding surface and having apredetermined throw or range of action so that its reverse actionrepositions the gage stop to determine on a later grinding of one lip anamount of reduction equal tothat produced on a previous grinding of theother lip, thereby bringing the point of the drill accurately into thecenter, said second adjusting means being an eccentric. and means forsetting the throw of said eccentric.

4. In a twist drill grinding machine, the combination with the grindlngsurface, a

drill guide casing mounted oblique to the grinding plane, a gage stoparranged to en gage the end of one lip opposite to the one being groundand a screw spindle for adjusting said guide casing to and from saidgrinding surface, of a second adjusting member adapted to adjust saidguide casing to and fromsaid grinding surface and having a predeterminedthrow of range of action, so that its reverse action reposltions thegage stop to determine on a later grind.- ing' of one lip an amount ofreduction equal to that produced on a previous grinding of the otherlip, thereby bringing the point of the drill accurately into the center,anIeccentric and means for adjusting the throw of said eccentric, saidmeans consisting of spring detents carried by said eccentric, andcooperating with a member having notches and spring stops cooperatingwith said notches for setting the,throw of said eccentric. L

In testimony whereof I aflix my signature.

CARL KOBIS.

